My analogy: You can think of email hosting similar to package delivery providers in the United States. There are many different ways to send/receive your email messages, just as there are many different delivery carriers (IE – USPS, UPS, FedEx, DHL etc).
What is it? The same principles can be said about email hosting, as website hosting above, but it pertains strictly to email communication.
My recommendation: I recommend G-Suite (by Google) and Office 365 (by Microsoft). G-Suite and O365 provide a suite of programs and applications, far greater than just email alone. They have tools and programs ready to help run your business more efficiently. I also recommend those two in particular because they have dedicated support teams for any issues that arise. They are built to serve your business now and as it grows into the future.